LIVER FUNCTIONS TESTS -1-

LIVER FUNCTIONS TESTS -1-

1. By Dr KHALED ALGARIRI CAMS- QASSIM UNIVERSITY March 2023 BIOCHEMICAL ASPECTS OF LIVER FUNCTION TESTS\ Part 1

2. INTRODUCTION The liver is a reddish brown wedge shaped organ with four lobes of unequal size and shape. A human liver normally weighs 1.44–1.66 kg (3.2–3.7 lb ). Liver function tests are blood tests used to help diagnose and monitor liver disease or damage. The tests measure the levels of certain enzymes and proteins in our blood. Some of these tests measure how well the liver is performing its normal functions of producing protein and clearing bilirubin, a blood waste product .

3. FUNCTIONS OF THE LIVER 1-Synthetic functions : synthesis of plasma proteins,cholesterol , triacylglycerol and lipoprotein 2-Metabolic function: protein metabolism, ketogenesis , TCA cycle , production of ATP 3-Detoxification & excretion: ammonia to urea, bilirubin, cholesterol, drug metabolites. 4- Homeostasis : blood glucose regulation 5-Storage function: Vitamin A,D,K,B12 6-Production of bile salts

4. Why it's done Screening: They are non invasive yet sensitive modality for liver dysfunction. Pattern of disease: They are helpful to recognize pattern of various diseases. Like being helpful in differentiating between acute viral hapatitis and various cholestatic disorders and chronic liver disease.(CLD) Assess severity : They are helpful to assess the severity and predict the outcome of certain diseases like primary biliary cirrhosis. Follow up: They are helpful in the follow up of certain liver diseases and also helpful in evaluating response to therapy like autoimmune hepatitis

5. CLASSIFICATION OF LIVER FUNCTIONS TESTS

6. 1.Serum bilirubin 2.Urine bilirubin 3.Urine and feacal urobilinogen 4.Urine bile salts 5.Dye excretion tests TESTS BASED ON EXCRETORY FUNCTION

7. TESTS BASED ON DETOXIFICATION FUNCTION Hippuric acid test Determination of blood ammonia

8. TESTS BASED ON SYNTHETIC FUNCTION Prothrombin time Protein time

9. TESTS BASED ON METABOLIC FUNCTION

10. ENZYMES IN DIAGNOSIS OF LIVER DISEASE SERUM TRANSAMINASES AST ALT ALP GGT 5’NT

11. 1.Serum bilirubin 2.Urine bilirubin 3.Urine and feacal urobilinogen 4.Urine bile salts 5.Dye excretion tests TESTS BASED ON EXCRETORY FUNCTION

12. Serum bilirubin Bilirubin: is the end product of heme degradation derived from breakdown senescent (aging) erythrocytes by mononuclear phagocytes system specially in the spleen, liver and bone marrow. The major pigment present in bile is the orange compound bilirubin.

13. Serum bilirubin It is highly soluble in all cell membranes (hydrophobic) and is also very toxic. Therefore, its excretion in the bile is one of the very important functions of the liver. Classification of bilirubin into direct & indirect bilirubin is based on original van den bergh method of measuring bilirubin.

14. Extravascular Pathway for RBC Destruction ( Liver, Bone marrow, & Spleen) Hemoglobin Globin Amino acids Amino acid pool Heme Bilirubin Fe 2 + Excreted Phagocytosis & Lysis Recycled The globin is recycled or converted into amino acids, which in turn are recycled or catabolized as required

15. BILIRUBIN METABOLISM Bilirubin is the excretory product formed by the catabolism of heme part of hemoglobin . Porphyrin part of heme are converted to bilirubin in reticuloendothelial cells of liver, spleen, bone marrow . Unconjugated bilirubin is bound to serum albumin &transferred to liver where it is conjugated to glucuronate by UDP GLUCURONYL TRANSFERASE. Conjugated bilirubin is excreted into bile. A fraction of bilirubin from stool is reabsorbed into blood via portal circulation ( enterohepatic circulation)

16. RBCs Breakdown Hemoglobin Produces & Breakdown Heme Biliverdin Bilirubin Heme Oxygenase Biliverdin Reductase

17. Bilirubin Is the Major Component of Bile Pigments, Steps of Execretion Hemoglobin is first dissociated into heme and globin. In the presence of NADPH and O 2 , the Heme oxygenase enzyme hydroxylates Heme and converts it into Biliverdin. Biliverdin is then reduced or converted into bilirubin by biliverdin reductase enzyme . Bilirubin is transported in blood bound to albumin forming a water soluble compound called hemobilirubin ( unconjugated bilirubin, free bilirubin ) which is rapidly transported to hepatocytes for further metabolism .

18. Role of Blood Proteins in the Metabolism of Bilirubin 1. Albumin Albumin Dissolved in Blood Bilirubin

19. Blood Liver Albumin Ligandin (-) charge Bilirubin Albumin Ligandin (-) charge Bilirubin Ligandin Prevents bilirubin from going back to plasma

20. 4-The liver removes bilirubin from the circulation rapidly, mediated by a carrier protein (receptor), and conjugates it with glucuronic acid. This reaction is catalyzed by the enzyme glucuronyl transferase in the smooth endoplasmic reticulum to have conjugated bilirubin , which is more water soluble than bilirubin. 5-The bilirubin- glucuronide (conjugated bilirubin) is secreted into the bile canaliculi . Note: the unconjugated bilirubin is normally not secreted. 6-In the small intestine, bilirubin glucuronide is poorly absorbed . In the gut, however, bacteria deconjugate it back to bilirubin, and convert it to the highly soluble colorless compound called Urobilinogen

21. 7- Only 20% of Urobilinogen can be absorbed by the small intestine ( this represents the enterohepatic circulation of bile pigments ). 70% of the Urobilinogen can be oxidized in the large intestine to Stercobilin and stercobilinogen (by bacteria). 10 % of Urobilinogen is excreted in either urine (where it is converted to yellow urobilin in the kidney) or feces (after it is converted to Stercobilin which is responsible for the brown color of feces). ( entero -hepatic circulation )

22. Insoluble in water Present normally in plasma Tightly complex to albumin Not filtered through renal glomeruli , is not excreted in urine Toxic substance The chief form of bilirubin in the blood Unconjugated Water soluble and Present normally in bile Loosely bound to albumin Filtered through renal glomeruli and excreted in urine Non-toxic Present in low concentration in the blood Conjugated Differences between the conjugated and unconjugated bilirubin

23. Diagnostic Importance of Bilirubin Disruption of bilirubin metabolism and excretion can cause hyperbilirubinaemia and subsequent jaundice Hyperbilirubinaemia maybe unconjugated (indirect) or conjugated (direct) depending on the type of bilirubin present in plasma.

24. A-Unconjugated Hyperbilirubinemia It is due to overproduction of bilirubin by reticuloendothelial system over the capacity of the liver to remove and clear from blood. It is characterized by high level of indirect or unconjugated bilirubin. This type of bilirubin can cross the blood-brain barrier into the central nervous system and cause kernicterus

25. Unconjugated hyperbilirubinemia occurs in the following conditions I-Neonatal or Physiologic Jaundice : This is the most common cause of jaundice in neonatal age. It results from accelerated hemolysis and immature hepatic system for uptake, conjugation and secretion of bilirubin . II-Hemolytic jaundice (Anemia)

26. III-Congenital Syndromes related to uptake and conjugation of bilirubin as follow : 1- Crigler-Najjar Syndrome Type 1: Due to severe decrease in the activity of UDP- glucuronyl transferase . Type II: Due to decreased activity of UDP- glucuronyl transferase that adds the second glucuronide group . 2- Gilbert Disease It is mainly due to hepatic defect in the uptake of bilirubin by liver cells. 3-Toxic Hyperbilirubinemia This is due to toxin-induced liver dysfunctions e.g. chloroform, carbon tetrachloride and mushroom poisoning .

27. B-Conjugated Hyperbilirubinemia Conjugated hyperbilirubinemia is due to reflux of direct or conjugated bilirubin into blood due to biliary obstruction , conjugated bilirubin is water soluble, so it is excreted in urine and darken its color.

28. Conjugated hyperbilirubinemia occurs in the following conditions 1-Obstructive Jaundice ( Cholestatic Jaundice) Conjugated hyperbilirubinemia results from blockage of hepatic or common bile duct (stones and tumors). 2- Micro-obstruction of intrahepatic biliary ductules by swollen damaged hepatocytes e.g. viral hepatitis and liver cirrhosis. Both cases are associated with marked increase of conjugated bilirubin and slight to moderate increase of unconjugated bilirubin (mixed hyperbilirubinemia )

29. 3- Rotor’s/ Dubin -Johnson syndrome – defective excretion of conjugated bilirubin into the biliary cannaliculi therefore elevated conjugated bilirubin

30. Jaundice becomes clinically evident when the serum bilirubin level exceeds 2.5mg/ dL . Several types of Jaundice: Hemolytic Hepatocellular Obstructive Symptoms: Yellow discoloration of the skin, sclera and mucous membranes Itching (pruritus) due to deposits of bile salts on the skin Stool becomes light in color Urine becomes deep orange and foamy

31. Normal range Bilirubin type Bilirubin level Total bilirubin 0.0-1.4 mg/ dL or 1.7-20.5 mcmol/L Direct bilirubin 0.0-0.3 mg/ dL or 1.7-5.1 mcmol /L Indirect bilirubin 0.2-1.2 mg/ dL or 3.4-20.5 mcmol /L

32. Hemolytic Increased rate of RBC destruction Increased Hb breakdown to bilirubin in RES Cells This exceeds the capacity of conjugation in liver. Hepatocellular Inability of hepatocytes to conjugate and/or excrete bilirubin. Obstructive Failure of excretion of conjugated bilirubin into the intestine, causing its regurgitation in circulation. Urinary and fecal urobilinogen are decreased Classification of Jaundice . According to etiology :

33. THANK YOU